Modern motor vehicles normally incorporate crumple zones, i.e. the regions or components of the vehicle which absorb energy by deformation in a collision, and thus protect other vehicle regions, such as in particular the occupants, from damage. Bumpers arranged at the front and rear in the direction of travel extend substantially transversely to the direction of travel. In a typical construction concept, the actual bumper or bumper cross-member is connected to a vehicle structure, e.g. the longitudinal members, by energy absorption elements (e.g. crash boxes, crash tubes or crumple boxes) which may also be called crumple elements. The bumper cross-member in itself, because of its design and/or the material used, may be designed more stably, while the energy absorption elements which extend approximately in the direction of travel are less stable. These may e.g. be made of aluminum or an aluminum alloy, and deform comparatively easily if a force is exerted thereon via the bumper. In particular, in frontal impacts at low speed, ideally the deformation can be substantially restricted to the energy absorption elements, while the vehicle structure remains undamaged to reduce the repair costs. The bumper may in some cases be configured integrally with the energy absorption elements. The actual connection to the vehicle chassis normally takes place via connecting plates which are welded to the energy absorption elements and can be connected to the vehicle structure e.g. a longitudinal member for example by bolting.
From safety aspects, SORB (small offset rigid barrier) collisions constitute a particular challenge. In these, the vehicle collides with an obstacle or another vehicle which is significantly offset to the vehicle center, wherein there is only a slight overlap. The actual impact may even take place outside the actual crumple element, so there is a danger that this absorbs only comparatively little energy, while the colliding obstacle can penetrate a long way, in some cases into the region of the front wheel. This may lead to further deformations which could extend as far as the vehicle interior. A fundamental problem in this context is that the part of the bumper cross-member which is arranged outside the crumple element—and hence in a SORB collision makes primary contact with the obstacle—deforms too easily to effectively absorb energy for example, or also to achieve a lateral deflection of the vehicle away from the obstacle. In the prior art, attempts have been made to eliminate this, firstly by the provision of deflection plates, impact plates or similar structures attached at the sides of the bumper cross-member, and secondly by a connection between the bumper cross-member (or side parts attached thereto) and a longitudinal member to which the bumper cross-member is connected by a crumple element. The latter measure aims to deflect the force action, wherein the cross-member is ideally deformed by a laterally acting force and thus absorbs energy. The problem with all these measures is that, firstly, the vehicle weight must not be increased excessively, and secondly the crash behavior in SORB collisions must not be improved to the detriment of the crash behavior in other situations. In other words, the additional or modified elements must not adversely affect the other crash behavior, in particular the function of the crumple elements.
US 2014/0312637 A1 and US 2014/0091585 A1 show an assembly of a vehicle with a longitudinal member and a bumper bar which has a bumper bar extension extending laterally outside the longitudinal member. Furthermore, the assembly comprises a connecting element which is connected by an inner connecting portion to the longitudinal member and by an outer connecting portion to the bumper. Said connections are formed as hinge connections, so that on a frontal impact, the connecting element can pivot relative to the bumper bar and the longitudinal member and serve to introduce a lateral force from the bumper bar into the longitudinal member, which leads to its deformation.
US 2014/0361559 A1 describes a front structure of a motor vehicle with a front element which is arranged on a longitudinal member and comprises an energy-absorbing portion, and a bumper bar to which the front element is attached. Furthermore, the structure comprises a first load transfer element which protrudes laterally outward from the front element on a rear side of the energy-absorbing portion, and a second load transfer element which protrudes from the front element on a front side of the energy-absorbing portion. On a collision with a small overlap region, it is provided that the energy-absorbing region is compressed, wherein the second load transfer element is moved against the first load transfer element, leading to a lateral deformation of the longitudinal member.
U.S. Pat. No. 9,010,845 B1 discloses a vehicle with a lateral support element, e.g. a longitudinal member, a bumper assembly connected thereto and extending in the transverse direction of the vehicle, and a movable connecting assembly extending between the support element and the bumper assembly. It consists of an inner and an outer connecting element which are pivotably connected together. A pivotable connection exists firstly with the bumper assembly and secondly with the support element. On a frontal impact, the two connecting elements—depending on the nature of the impact—may pivot relative to each other to varying extents. The two elements pivot so far that they lie against each other and a lateral force is transmitted to the support elements. The support elements deform on a small overlap impact with a rigid barrier.
US 2015/0137556 A1 discloses a deflection plate arrangement for a vehicle with a bumper and a longitudinal member. The arrangement comprises a deflection plate which extends from laterally outside the bumper up to an outer end and returns to a rear end in the vicinity of longitudinal member, a guide element is attached to the rear end and has a guide face extending in the longitudinal direction, and a carrier attached to the longitudinal member and received by the guide element. On a frontal impact, the carrier (which e.g. may be configured as a roller) and the guide face (which e.g. may be configured as a guide rail) cooperate to guide the rear end. The deflection plate arrangement allows a lateral deflection of the vehicle on an impact with small overlap, but at the same time does not detract from the function of a crumple box.
U.S. Pat. No. 8,733,823 B2 discloses a bumper system for a motor vehicle with a cross-member arranged transversely to the direction of travel and two longitudinal members arranged parallel to the direction of travel, wherein the cross-member is connected to the longitudinal members directly or by means of a coupling element. The cross-member has two connecting portions for connecting to the longitudinal member or to two coupling elements, a center portion between the connecting portions, and two end portions which terminate the cross-member towards the vehicle sides. The cross-member is designed to fold with one end portion in the event of a frontal impact with small overlap, wherein said portion rests on a deformation element arranged behind it.
DE 10 2007 017 857 A1 describes a bumper assembly for a motor vehicle with a bumper cross-member running transversely to the longitudinal members of the vehicle and comprising a center portion and end portions which protrude beyond the longitudinal members and are curved or chamfered towards the rear. Each end portion at its outer end has a retaining element oriented in the transverse direction of the vehicle to limit sliding the obstacle from the respective end portion on an impact with small overlap. The end portion of the retaining element has an S-shaped profile.
US 2015/0097394 A1 discloses a front assembly of a motor vehicle with a chassis longitudinal member, a bumper bar arranged in front of this, an impact plate and a gripper bracket. The impact plate comprises a front leg which extends outside of and is attached to the bumper bar, and a rear leg extends from an outer end of the front leg to the chassis longitudinal member. The gripper bracket is attached to the chassis longitudinal member behind the rear leg. On a frontal impact, the rear leg slides to the rear along the longitudinal member until it hits the gripper bracket, which stops its movement.
In the context of the prior art outlined above, the provision of a bumper unit with optimized crash behavior in relation to frontal impacts with small overlap without adversely affecting crash behavior for impacts with greater overlap, leaves room for improvement.